C# 5.0 Programmer's Reference

360 ❘ CHAPTER 16 Printing
When you master the basic concepts, printing is mostly a matter of learning how to draw graphics.
Drawing graphics in a Windows Forms application is practically the same whether you’re drawing
on a form, PictureBox, or printed page.
The following section describes the basic process. The sections after that explain how to print specific
items, such as text, images, and shapes. The final Windows Forms example shows how to display
page numbers, change margins for odd and even pages, and split paragraphs across multiple pages.
Basic Printing
The heart of the printing process in Windows Forms applications is the PrintDocument object. As
its name implies, it represents a document to be printed.
You might expect the PrintDocument class to provide methods that you call to draw text, images,
lines, and other items on the document. The process actually works in reverse. The program creates
a PrintDocument object. It then directly or indirectly tells the object that it wants to generate a
print preview or an actual printout. The PrintDocument then raises events asking the program what
it should draw on each page of the printout. The program responds with drawing commands that
determine the results.
Perceptive Printing
This process of the PrintDocument object raising event seems backward but it’s
actually fairly clever. The PrintPage event, which is described in detail shortly,
passes the program a Graphics object on which to draw. This is the same kind
of Graphics object that a program uses to draw on a Form, PictureBox, Bitmap,
or anything else in .NET. By giving you a Graphics object, the PrintPage event
enables you to use the same kind of code you use to draw anywhere else.
In fact, if you design the program properly, you can use the same code to draw on
a Form, PictureBox, and printout. If you place all your drawing commands in a
method that takes a Graphics object as a parameter, you can use that method to
generate results for the screen or the printer.
When a PrintDocument object must perform printing-related tasks, it raises four key events:
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BeginPrint—The PrintDocument raises its BeginPrint event when it is about to start
printing. The program can initialize data structures, load data, connect to databases, and
otherwise get ready to print.
QueryPageSettings—Before it prints a page, the PrintDocument object raises this event.
The program can catch this event and make changes that are specific to the page it is about
to print. For example, if you are printing a booklet, the program can adjust the margins to
leave extra space on the side of the page where the staples will be.
PrintPage—The PrintDocument object raises the PrintPage event to generate a page.
The program catches this event and uses the e.Graphics parameter to generate output. After
it finishes printing the page, the program should set the value e.HasMorePages to true or
false to tell the PrintDocument whether there are more pages to print after this one.
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